ge jvm

Export JVM memory information on CentOS, and export jvm memory from centosFirst, check the Tomcat process Id: [root@iZ25Z ~]# ps aux | grep javawww 2111 4.0 23.5 1637648 452756 ? Sl 10:12 4:35 /usr/java/jdk1.7.0_80/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties ...　　We can see that the Tomcat process Id is 2111, and then use the JDK built-in tool jmap to e

Error: cocould not open... jvm. cfg solution, cocould... jvm. cfgThis is mostly because JDK has been installed on the computer. After you uninstall and reinstall it, an error occurs when you run the java command: cocould not open... jvm. cfg. Open the system environment variable and view the PATH. The following configuration information is displayed: % SystemRoot

Pgc:perm generation (bytes)S0: The first survivor (Survivor area) of the young generation has been used as a percentage of current capacityS1: The second survivor (Survivor area) in the younger generation has been used as a percentage of current capacityE: Eden (Eden) in the young generation has been used as a percentage of current capacityPercentage of current capacity used by O:old generationPercentage of current capacity used by P:perm generationS0CMX: Maximum Capacity (bytes) of the first S

) { e.printStackTrace(); } } } Public class T implements Runnable { Public void Run() {A A =NewA (); System.out.println (Thread.CurrentThread (). GetName () +" "+NewDate ()); } Public Static void Main(string[] args) {T T1 =NewT (); T t2 =NewT (); Thread Thread1 =NewThread (t1); Thread thread2 =NewThread (T2); Thread1.start (); Thread2.start (); } }The results of the operation are as follows: Thread-0 Fri Dec 10:25:00 CST 2013Thread-1 F

class execution mechanism The JVM executes class bytecode based on the stack architecture, and after the thread is created, the program counter (PC) and stack (stack) are generated. The PC holds the offset of the next executed instruction within the method, the stack holds a stack frame, each stack frame corresponds to each call of each method, and the stack frame holds local variables and the operand stack The structure of the stack

JVM-class file full parsing-method table set, jvm-class setMethod table set The previous magic number, minor version number, main board number, constant pool entry, constant pool, access flag, class index, parent index, interface index set, and field table set, then the method table will be followed. The method table is constructed like a field table, which contains several items in sequence: access_flags,

JVM-class file full parsing-Attribute Table set, jvm-class setAttribute Table set In front of magic number, minor version number, main board number, constant pool entry, constant pool, access flag, class index, parent index, interface index set, field table set, method table set, the next step is the set of attribute tables. In the class file, field tables, and method tables, you can carry your own attribu

JVM-concurrency-Java memory model, jvm-concurrency-java modelJava Memory Model (1). Master memory and working memory The Java Memory Model specifies that all variables are stored in the primary memory. Copies of the primary memory of each type of thread variables. All operations (read operations, value assignment operations, etc.) of the thread on the variables must be performed in the working memory, rathe

Jvm theory-constant pool-string, jvm constant pool-string String constant pool-constant item (Cp_info) Structure CONSTANT_String_info {u1 tag = 8; u2 string_index; // store CONSTANT_Utf8_info pointer} CONSTANT_Utf8_info {u1 tag = 1; u2 length; // byte array length u1 bytes [length]; // UTF-8 encoded byte array} Case 1 Public class StringDemo {private String s1 = "String S1 ";} Javac StringDemo. java Javap-

Deep understanding of JVM Reading Notes Mind Map, deep understanding of jvm Reading Notes To prove that I have completed this book and bought a new book, I don't have to worry about it... After 8 minutes of brain image, I feel that the entire person is not good. T_T brain cells do not know the number of dead cells... In fact, it is not thoroughly understood. It is estimated that we will open it again in a f

JVM memory structure --- deep understanding of Java Virtual Machine (jvm) When executing a Java program, the Java Virtual Machine divides the memory it manages into several different data regions. These regions have different purposes and create and destroy data independently based on their respective execution rules. Virtual Machine memory Division ,: The regions with independent threads are as follows: V

JVM-runtime data zone and JVM-runtime data ZoneRuntime data Zone1. Program Counter Register: it is a small memory space and can be seen as a line number indicator of the bytecode executed by the current thread. --> The bytecode interpreter selects the next bytecode instruction to be executed by changing the value of this counter, the basic functions such as branch, loop, jump, exception handling, and thread

The JVM is the heavy load machine behind Java features and performance, which most developers take for granted. However, few of us understand how the JVM works-like task assignments and garbage collection, turning threads, opening and closing files, interrupting and/or JIT compiling Java bytecode, and so on. Not being familiar with the JVM will not only affect a

Java.lang.OutOfMemoryError:PermGen Space Found that many people attribute the problem to: Spring,hibernate,tomcat, because they generate classes dynamically, causing permanent heap overflow in the JVM. Then there is a divergence of opinions about how to upgrade the Tomcat version to the latest or even simply without Tomcat. There are also questions about spring that are hotly discussed at the Spring Forum, because spring's use of cblib in AOP creates

Internal structure diagram of the JVM Java virtual machines are mainly divided into five areas: Method area, Heap, Java stack, PC register, local method stack. BelowSee some important questions about the structure of the JVM. 1. Which areas are shared? Which ones are private? Java stacks, local method stacks, and program counters are created and destroyed with the start and end of user threads.Each thr

JVM Memory Model The memory space of the Java Virtual machine (Java MACHINE=JVM) is divided into five parts, respectively:1. Program counter2. Java Virtual machine stack3. Local Method Stack4. Heap5. Method area. The following is an in-depth introduction to these five regions.1. Program Counter 1.1. What is a program counter. A program counter is a small memory space that can be viewed as the line number i

Deep understanding of the memory management mechanism of JVM Notes Runtime data Region program counter JVM stack local method stack Java heap method area run frequent pool Direct Memory object access OutOfMemoryError exception Java heap overflow sample JVM stack and local method stack overflow run frequent pool overflow native Direct Memory Overflow deep understa

Brief IntroductionJava.exe is the execution program of the Java classfile. An execution shell that loads JVM. dll (in windows, the following uses Windows as an example, Linux and Solaris are actually similar, for: libjvm. So), this dynamic Connection Library is Java The actual operation of the virtual machine. This document describes how the java. exe program finds and loads JVM. dll. Dynamic library, and c

GC mechanism: Allocating an object using the new keyword; when releasing an object, the program cannot access the object again, as long as it is assigned NULL to all references to the object, and we call the object "unreachable." The GC is responsible for reclaiming the memory space of all "unreachable" objects. JVM Tuning Method: 1. The most basic advice is to release the references to unwanted objects as soon as possible. Most programmers use tempor

The JVM is a virtual machine and a specification, and he follows the design principles of the von Neumann architecture. Von Neumann architecture, it is pointed out that the computer processing data and instructions are binary number, using stored procedures to store in the same memory without distinction, and sequential execution, instruction by the operation code and address code, the operation code determines the type of operation and the number of